ACDSeePrint Job

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Serbian Dental J, 2008, 55

UDC: 616.314.21-007-089.844:004.4

ISSN 0039-1743

COBISS. SR-ID 8417026

Layered Additive Manufacturing in Clinical Medicine DOI: 10.2298/SGS0804259D

Slojevita aditivna proizvodnja u kliničkoj medicini Igor Drstvensek1, Natasa Ihan Hren2, Tadej Strojnik3, Vojko Pogacar1, Hartner T Zupanci1c, Andreja Sinkovic4 1 University of Maribor, Faculty of Mechanical Engineering, SI-2000 Maribor, Slovenia 2 University of Ljubljana, Medical faculty, Department of maxillofacial and oral surgery, SI-1000 Ljubljana, Slovenia 3 University Clinical Centre Maribor, Department of Neurosurgery, SI-2000 Maribor, Slovenia 4 University Clinical Centre Maribor, Department of Medical research, SI-2000 Maribor, Slovenia

PRIKAZ IZ SLUČAJA (PP) CASE REPORT

SUMMARY

KRATAK SADRŽAJ

The use of contemporary technologies of Computer Assisted Design (CAD), combined with latest rapid prototyping, tooling and manufacturing, with traditional CT scanning techniques and high medical skills are used as instruments for better diagnostic visualization, simulation of procedures and treatment of patients with craniofacial deformities. They also improve the overall performances of medical and nursing staff thus influencing the quality of medical service. Patients with congenital defects, orthognathic deformities, deformities after malignancy treatment or after craniofacial traumatic injuries of different severities are of particular interests due to both aesthetic and functional alterations. The paper presents two clinical cases – a patient with scull bone defect after brain hemorrhage and brain edema as well as a patient with hemifacial microsomia treated by surgery followed by implantation of titanium angular implant prepared by means of computer tomography scans, Computer Aided Design and Rapid Manufacturing technologies.

Savremene tehnologije dizajniranja uz pomoć kompjutera (CAD) u kombinaciji sa najnovijim brzom izradom prototipa, modeliranjem i izradom sa tradicionalnim CT tehnikama skeniranja i usavršenim medicinskim veštinama koriste se kao instrumenti za bolju vizualizaciju, simuliranje terapeutskih procedura kod pacijenata sa kraniofacijalnim deformitetima. Oni takođe unapređuju ukupni učinak medicinskog i pomoćnog osoblja i tako utiču na kvalitet medicinskih usluga. Pacijenti sa kongenitalnim defektima, ortognatskim deformitetima, deformitetima posle terapije maligniteta ili kraniofacijalnih trauma su od naročitog interesa u ovoj oblasti zbog estetskih i funkcionalnih poboljšanja. Ovaj rad prikazuje dva klinička slučaja – pacijenta sa defektom lobanje posle moždane hemoragije i edema mozga, kao i pacijenta sa hemifacijalnom mikrozomijom rešavanom hirurškim putem posle čega je urađena ugradnja titanijumskog angularnog implanta urađenog pomoću CT skeniranja, kompjuterom-vođenog dizajna i tehnologijom brze proizvodnje.

Key-words: rapid prototyping, computer assisted design, maxilla, scull, reconstructive surgery

Ključne reči: brza izrada prototipa, kompjuteromvođen dizajn, maksila, lobanja, rekonstruktivna hirurgija.

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Stom Glas S, vol. 55, 2008

Introduction

Uvod

Defects in the craniofacial skeleton such as congenital defects, orthognathic deformities or accidental injuries, resulting from trauma, infection, malignancies, etc. need reconstruction to achieve the primary function of the injured skeleton. Cranio-facial reconstruction is demanding since it affects the facial region, being highly exposed to visual appearance, and thus influencing psychological state and social life. However, in aesthetic rehabilitation, where the efforts are focused to attain at least approximate normal appearance, reconstructions are often very difficult with patients' own tissues1. Surgical treatment of patients after caraniofacial injures due to trauma or a disease results in deformities, usually requiring an implantation of either an autologoustissue or biocompatible/biodegradable implants that replace missing parts of the tissue, usually bone. Autologous-tissue implants are always the first choice if available. The bone defects in maxillofacial region can be replaced by patients’ own bone by different surgical procedures such as bone grafts or by distraction osteogenesis1. These different autogenous bone grafts are “golden standard” for reconstruction procedures because they provide osteogenic cells, but they are of limited quantity and connected with risk of complications on donor site2,3. In cases where autologous material can not be obtained an artificial implant has to be made to fullfill physical, aesthetical and functional demands4. The implant market mainly covers areas of serial implant, and biocompatible material production. Serial implants are predominantly used in orthopedics as functionality is of main importance. In cranio-maxilo-facial surgery implants also have to fulfill an aesthetic function. Therefore, their serial production is limited. Modern synthetic facial implants made of modern plastic materials (acrylates) are in the shape of contoured two-piece chin implants and angular mandible augmentation implants, where the synthetic material needs to have following properties: biocompatibility, inertness, bone-similar weight or even lighter, capability to generate no artefacts on computer tomography (CT) and magnetic resonance (MT) scans, ease of manufacturing, enough strength to resist functional stress, not expensive and without thermal conductivity3-5. The production of such implants starts by capturing a three-dimensional data set of the problematic area (skull, face, mandibular area...) by transforming sets of CT or MRI two-dimensional pictures into a threedimensional, digital, model. This model is then used as the basis on which modelling of the defective – missing area The5,6finished . digital model is then manufactured ustakes place ing one of the Rapid Prototyping (RP) or Rapid Manufacturing (RM) technologies. RM products are usually made of titanium or cobalt – chrome alloys, being at the moment the only biocompatible materials available for RM technologies that can be directly used as implants.

Defekti kraniofacijalnog skeleta kao što su kongenitalni defekti, ortognatski deformiteti, deformiteti nastali usled povreda, infekcija, maligniteta itd. zahtevaju rekonstrukciju da bi se uspostavila primarna funkcija povređenog dela skeleta. Kraniofacijalna rekonstrukcija je zahtevna jer uključuje facijalni region, koji je vizuelno eksponiran i utiče na psihološko stanje i socijalni život. Međutim, u estetskoj rehabilitaciji gde su napori usmereni ka vraćanju približno prvobitnog izgleda, rekonstrukcije pacijentovim tkivima su često veoma teške.1 Hirurški tretman pacijenata sa kraniofacijalnim provredama i defektima usled infekcija rezultiraju deformitetima koji obično zahtevaju implantaciju bilo autolognog tkiva ili biokompatibilnog/biorazgradljivog implanta kojim se zamenjuje nedostajuće tkivo, obično kost. Autologni tkivni implanti su uvek prvi izbor ako je to moguće. Koštani defekti u maksilofacijalnoj regiji mogu se zameniti pacijentovom kosti različitim hirurškim procedurama kao što su koštani graftovi ili distrakciona osteogeneza.1 Ovi različiti autologni koštani graftovi su „zlatni standard“ u rekonstruktivnim procedurama jer obezbeđuju osteogene ćelije, ali su kvantitativno limitirani i praćenim mogućim komplikacijama u donor regionu.2,3 U slučajevima kada se autologni materijal ne može obezbediti, arteficijalni implant se mora izraditi da ispuni fizičke, estetske i funkcionalne zahteve.4 Tržište implanata trenutno pokriva oblasti serijskih implanata i proizvodnju biokompatibilnih materijala. Serijski implanti se pretežno koriste u ortopediji gde je funkcionalnost najvažnija. U kraniomaksilo-facijalnoj hirurgiji, serijski implanti takođe ispunjavaju estetsku funkciju. Zbog toga je njihova serijska proizvodnja ograničena. Savremeni sintetski facijalni implanti izrađeni su od savremenih plastičnih materijala (akrilata) kao oblikovani dvodelni implanti brade i angularni implanti za mandibularnu augmentaciju, a sintetski materijal treba da ima sledeće osobine: biokompatibilnost, inertnost, težinu sličnu ili manju od kosti, zatim da ne daje artefakte na CT-u i NMR-u, da je jednostavan za proizvodnju, dovoljno jak da se odupre funkcionalnom stresu, jeftin i da je termoizolator.3-5 Proizvodnja takvih implanata počinje prikupljanjem 3D podataka kritične regije (lobanje, lica, mandibule...) transformacijom CT ili NMR 2D slika u 3D digitalni model. Ovaj model se zatim koristi kao baza za modeliranje defektne/nedotajuće regije.5,6 Završen digitalni model se zatim proizvodi primenom Brze izrade prototipa (BIP) ili Tehnologija brze izrade (TBI). TBI proizvodi su obično od titanijuma ili kobalt-hrom legure, i trenutno su jedini biokompatibilni materijali dostupni za TBI, a koji se mogu direktno koristiti kao implanti.

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RP products are used as patterns for further processing using one of the Rapid Tooling (RT) techniques, including Silicone Rubber Moulding (SRM)6. Our aim was to present two cases, treated by surgery followed by implantation of implants prepared by means of computer tomography scans, Computer Assisted Design and Rapid Manufacturing technologies.

BIP proizvodi se koriste kao obrasci za buduće procesiranje primenom Tehnika brze obrade (TBO) koje obuhvataju i Modeliranje silikonskom gumom (MSG).6 Ovaj rad prikazuje dva slučaja rešavana hirurškim putem a zatim ugradnjom implanata pripremljenih uz pomoć CT skeniranja, kompjuterom-vođenog dizajniranja i tehnologija brze izrade.

Case 1

Slučaj 1 Tridesetčetvorogodišnji pacijent je primljen na Neurohirurgiju zbog spontane intracerebralne hemoragije. Pacijentu je odmah urađena kraniotomija posle koje je evakuisan intracerebralni hematom. Istovremeno, postavljena je sonda za intrakranijalni pritisak. Kad se intrakranijalni pritisak povećao, urađen je kontrolni CT snimak kojim je otkriven edem mozga. Uprkos svim naporima, intrakranijalni pritisak nije mogao biti kontrolisan konzervativnim metodama. Urađena je angiografija kojom je otkriven smanjen protok krvi kroz levu hemisferu. Zbog toga je doneta odluka da se uradi dekompresivna kraniektomija. Posle intervencije, intrakranijalni pritisak je mogao biti bolje kontrolisan i pacijentovo stanje je počelo da se popravlja, ali je ostao veliki koštani defekt lobanje. Pacijentovo stanje i svest su se postepeno poboljšavali, pa je on kasnije prebačen na institut za rehabilitaciju gde je urađena kompleksna neuro-rehabilitacija. Posle toga je urađena kranioplastika sa polimetil-metakrilatom (PMMA) u obliku koštanog cementa da bi se nadoknadio deo lobanje.6,8 (Slike 1-2)

Thirty four year old male patient was admitted to Neurosurgery due to spontaneous intracerebral haemorrhage. The patient was immediately treated surgically with craniotomy, and intracerebral hematoma was evacuated. At the same time an intracranial pressure (ICP) probe was inserted. When ICP increased, control CT scan was performed. It revealed brain edema. Despite all efforts ICP could no longer be controlled by conservative measures. Angiograpy was performed showing decreased blood flow in the left hemisphere. Therefore a decision was made to perform a decompressive craniectomy. After intervention the ICP was better controlled and patient’s state started to improve, leaving a large bone defect in the scull. His condition and awareness started to improve gradually. Later he was transferred to the rehabilitation institute where he received complex neuro-rehabilitation. After rehabilitation cranioplasty with poly-methyl-metaacrylat (PMMA) in the form of bone cement, was carried out to replace the missing part of the skull6,8 (Figure 1, Figure 2).

Figure 1. Three-dimensional (3D) reconstruction of the scull from ICON data Slika 1. Trodimenzionalna (3D) rekonstrukcija lobanje pomoću ICON podataka.

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Figure 2. Model of the scull and the scull implant Slika 2. Model lobanje i implanta.

Case 2 Twenty four year old mentally healthy man was born with hemifacial microsomia. This is a severe asymmetry of facial bone and soft tissues in vertical, sagital and transverse plane combined with hearing impairment on the affected side. He wasn’t treated before his adulthood; all surgical procedures were done in Clinical department of maxillofacial and oral surgery, University clinical centre Ljubljana. He was treated by classical ortognathic surgical procedures and by a modern surgical technology as distraction osteogenesis of mandible. The first surgical procedure produced vertical part of his left lower jaw by distraction osteogenesis. Than his upper jaw was elongated and rotated by LeFort I osteotomy and his autogenous bone grafting. After these surgical procedures the remaining defect of the bone and soft tissues was partially substituted with on-lay xenogenic graft (Medpore mandible on-lay graft) because of the transverse discrepancy, but it was removed after more than one year because of inflammation and replaced by titanium angular implant, which was prepared on the basis of computer tomography (CT) scans, Computer Aided Design (CAD) and Rapid Manufacturing technologies (Figure 3, Figure 4).

Slučaj 2 Dvadesetčetvorogodišnji mentalno zdrav čovek je rođen sa hemifacijalnom mikrozomijom. To je stanje izražene asimetrije facijalnih koštanih i mekih tkiva u vertikalnoj, sagitalnoj i transverzalnoj ravni udruženo sa oslabljenim sluhom na defektnoj strani. Pacijent nije lečen pre svoje odrasle dobi; sve hirurške procedure su urađene na Kliničkom odseku za maksilofacijalnu i oralnu hirurgiju, Univerzitetskog kliničkog centra u Ljubljani. Pacijent je lečen klasičnim ortognatsko-hirurškim procedurama i savremenom hirurškom tehnologijom kao što je distrakciona osteogeneza mandibule. Prvom hirurškom intervencijom, distrakcionom osteogenezom, rekonstruisana je vertikalna dimenzija pacijentove leve strane mandibule. Zatim je maksila elongirana i rotirana primenom LeFort I osteotomije i autogenim koštanim graftom. Posle ovih hirurških procedura, preostali defekt kosti i mekih tkiva ja delimično nadoknađen on-lay ksenograftom (Medpore mandibularni on-lay graft) zbog transverzalne diskrepance, ali je ukonjen posle godinu dana zbog inflamacije i zamenjen titanijumskim angularnim implantom, urađenim na bazi CT snimaka, kompjuterom-vođenog dizajna (CAD) i tehnologije brze izrade. (Slike 3-4)

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Figure 3. Reference shape of the mandibular implant for implant design Slika 3. Referentni oblik mandibularnog implanta za dizajn implanta.

Figure 4. Virtual model of the mandibular implant Slika 4. Virtuelni model mandibularnog implanta.

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Discussion

Diskusija

In last few years several trials demonstrated the potential of virtual modelling and rapid prototyping in clinical medical praxis. Cranial and maxillofacial areas are very suitable for these technologies due to relatively low mechanical stresses that occur in this area and due to significant impact of aesthetical demands 4,5,9. During last few years, our group developed two different types of implants, that were implanted in patients. The first one was a cranial implant implanted to a patient suffering from spontaneous intra cerebral haemorrhage and the second one a mandibular implant, fulfilling the aesthetical anf function demands of the face. In the first case PMMA was used to manufacture the implant indirectly, using the SRM to shape the PMMA. The last was produced directly out of Titanium alloys, using selective laser melting equipment (EOS M270, Central University of Technology, Free State, South Africa). The easiest way to reconstruct the structure of a patient’s bones was to use those CT images that already existed from previous treatments of the patient. A set of CT images was converted into a three-dimensional, digital model using one of the available conversion software, such as Mimics (Materialise), RapidForm (Inus Technology), 3D doctor (Able Software), Amira (Marcury Computer), or others10. The input to this software was usually in the form of DICOM files and output was predominantly Standard Tessellation Language (STL), which could be directly used in most RP technologies to produce real models. But it could also be manipulated by special softwares such as Magics (Materialise), RapidForm, PolyWorks (InnovMetric). Combining these software and STL models of scanned body parts, missing tissue could be modelled and saved as new STL files, afterwards further processed or used for the production of real implant models by means of RP technologies5,6. Reconstructed models of the skull in both cases were manufactured using selective laser sintering. The method was chosen to produce skull models, since this technology produces rigid and resistable polyamide parts and the material is relatively cheap11. SLS rapid prototyping technology builds parts from powder that is solidified in slices by a laser beam. The powder is usually a plastic compound, or metallic and ceramic powders5,6. CAD modelling of the cranial implant was performed using several reverse engineering software packages. The basic idea was to mirror the entire skull and then perform the Boolean operation of subtracting the original skull from the mirrored one, resulting in a three-dimensional model of the implant. Possible asymmetry of the implant was avoided by the use of three-dimensional animation software. However, we observed that in a case of smaller parts such as the implant for cranioplastic or maxillofacial surgery SLS models were too rough especially if the model was intended to be used as a prime part for silicone rubber mould production12. Because of its better performance in terms of surface and dimensional quality a PolyJet procedure was used to produce the implants’ models.

U poslednjih nekoliko godina, nekoliko studija je pokazalo potencijal virtuelnog modeliranja i brze izrade prototipa u kliničkoj medicinskoj praksi. Kranijalna i maksilofacijalna oblast su vrlo pogodne za ove tehnologije zbog realitvno malog mehaničkog stresa kome su izložene ali i velikog uticaja estetskih zahteva.4,5,9 U poslednjih nekoliko godina, naša grupa je razvila dva različita tipa implanata. Prvi je kranijalni implant koji je ugrađen pacijentu sa spontanom intracerebralnom hemoragijom, a drugi je mandibularni implant, koji je trebalo da ispuni estetske i funkcionalne zahteve lica. U prvom slučaju, PMMA je korišćen za indirektnu izradu implanta primenom MSG za oblikovanje PMMA. Drugi je proizveden direktno od titanijumske legure korišćenjem selektivnog laserskog topljenja (EOS M270, Centralni Tehnološki Univerzitet, Free State, Južna Afrika). Najjednostavniji način za rekonstrukciju koštanih struktura bio je uz pomoć CT snimaka koji su urađeni u toku prethodnog lečenja pacijenta. Set CT snimaka je konvertovan u 3D digitalni model pomoću softvera za konverziju kao što su Mimics (Materialise), RapidForm (Inus Technology) 3D doctor (Able Software), Amira (Marcury Computer) i drugi.10 Ulazni podaci za ovakav tip softvera su obično u obliku DICOM podataka dok je izlaz pretežno u vidu Standard Tessellation Language (STL) koji se može koristiti direktno u većini BIP tehnologija za izradu modela. Međutim, on se može koristiti i u specijalnim tipovima softvera ako što su Magics (Materialise), RapidForm, PolyWorks (InnovMetric). Kombinovanjem ovih metoda i STL modela skeniranih delova tela, nedostajuće tkivo se može modelirati i sačuvati u obliku novog STL dokumenta, posle čega se može kasnije dorađivati ili koristiti za izradu implantnih modela BIP tehnologijama.5,6 Rekonstruisani modeli lobanje kod oba pacijenta su izrađeni primenom selektivnog laserskog sinterovanja. Ovaj metod je odabran za izradu modela lobanje, jer se ovom tehnologijom mogu izraditi rigidni i otporni poliamidni delovi, a materijal je relativno jeftin.11 SLS BIP tehnologijom se prave delovi od praha koji očvršćava po slojevima uz pomoć lasera. Prah je obično plastično jedinjenje, a može biti i metalni ili keramički.5,6 CAD modeliranje kranijalnog implanta je urađeno pomoću nekoliko inženjerskih softverskih paketa. Osnovna ideja je bila da se modelira defektna lobanja, a zatim primenom Boolean operacije oduzme originalna lobanja od defektne, čime ostaje samo 3D model implanta. Moguća asimetrija implanta je izbegnuta primenom 3D softvera za animaciju. Međutim, primetili smo da su SLS modeli previše grubi za manje delove kao što su implanti za kranioplastičnu ili maksilofacijalnu hirurgiju, posebno ako je model namenjen kao primarni deo za MSG proizvodnju.12 Zbog boljeg kvaliteta površine i dimenzija, PolyJet procedurom je izrađen model implanta od fotopolimernih smola.


PolyJet rapid prototyping technology built models from photo polymeric resins. Each layer was jetted on the work tray by a printing head and then cured by ultraviolet light. The support material was later removed by a water jet. Real models of the skull and the implant were then used for testing dimensional accuracy and as a communication tool between the engineer and the medical doctor during the phase of operation planning. A modified SRM procedure was used for the production of biocompatible implant. A SRM was made using a normal frame to hold the silicone and the pattern11. Pattern-holders were purposely made out of 5mm steel wires in order to make some room for excess PMMA compound. The usual casting of material through a round-gate was impossible because of its high viscosity. The plan was to prepare a mixture in the lower part of the tool and then cover it with the upper part. Therefore the mould had to be modified in order to use it as a press. This required preparation of “glides” for improved leading of the tools and to prevent side movements that could lead to improper formation of the implant. At first, experiments showed that the initial release openings were misspositioned and too small. The produced implant was too thick and uneven compared to the RP model. Therefore, the mould was modified with some extra release openings. Afterwards the experiment was repeated and the results were much better. Unfortunately, it is impossible to use an exact required amount of the material since the bone cement comes in preset quantities for both sterile components and require use of the whole amounts of both components to avoid lagging of residual monomers, as a consequence of insufficient mixing ratio. Residual monomers are highly poisonous and can, among other consequences, cause heart arrhythmia, as well as cardiac arrest. The excess amount of material forms certain extra features in the parting plane of the mould that have to be manually removed after moulding. The surgical procedure was a standard procedure. The implant was inserted into the skull of the patient and fixed by titanium plates and screws. But the duration of the the surgical procedure was shortened for approximately 50% due to preparation work (planning, fit and function testing) done before the operation. In our second case the treatment of the patient with hemifacial microsomia had the goal to achieve bone symmetry as well as to substitute the soft tissue defect4. In preparing mandibular implant bacterial colonization was of particular concern. Because of the inflammation that developed on Medpore mandible on-lay graft, an implant was manufactured, consisting of the material not allowing bacteria to develop, but still providing adequate symmetrical reconstruction of the face to get the physiologic functions as well as an aesthetic appearance.

265 Svaki sloj je izbrizgan na radnu površinu, a zatim polimerizovan UV svetlom. Potporni materijal je kasnije uklonjen vodenim sprejom. Realni modeli lobanje i implanti su, zatim, testirani u smislu dimenzionalne preciznosti i kao sredstvo komunikacije između inženjera i lekara u fazi planiranja. Modifikovana MSG procedura je primenjena za izradu biokompatibilnog implata. Kalup od silikonske gume je izrađen korišćenjem običnog rama za držanje silikona i matrice. 11 Ovi držači matrice su namerno izrađeni od čeličnih žica 5 mm u prečniku da bi se napravio prostor za višak PMMA. Uobičajeno izlivanje matrijala bilo je nemoguće zbog izražene viskoznosti. Plan je bio da se pripremi mešavina u donjem delu i zatim prekrije gornjim delom. Zbog toga je kalup morao biti modifikovan da bi se mogao koristiti kao presa. Ovo je zahtevalo pripremu „klizača“ za bolje vođenje i prevenciju bočnih pokreta koji bi doveli do nepravilne izrade implanta. U početku je primećeno da su otvori pogrešno pozicionirani i premali. Izrađen implant je bio predebeo i nejednak u poređenju sa BIP modelom. Zato je kalup modifikovan dopunskim otvorima. Posle toga eksperiment je ponovljen i rezultati su bili mnogo bolji. Nažalost, nemoguće je odmeriti tačnu količinu materijala koja je potrebna, jer je koštani cement u već pripremljenim količinama za sterilne komponente i zahteva upotrebu celokupne količine da bi se izbeglo zaostajanje rezidualnih monomera zbog neadekvatnog odnosa pri mešanju. Rezidualni monomeri su visoko toksični i mogu, između ostalog, izazvati srčanu aritmiju i infarkt. Višak materijala morao je biti ručno uklonjen nakon izrade kalupa. Hirurška procedura je bila uobičajena. Implant je ugrađen u lobanju pacijenta i fiksiran titanijumskim pločicama i zavrtnjima. Međutim, trajanje procedure je skraćeno za oko 50% zbog prethodne pripreme (planiranje, probe i funkcionalni testovi). U našem drugom slučaju, terapija kod pacijenta sa hemifacijalnom mikrozomijom imala je za cilj postizanje koštane simetrije i nadoknadu mekog tkiva. 4 U toku pripreme mandibularnog implanta, bakterijska infekcija je bila od velikog značaja. Zbog zapaljenja koje se razvilo na Medpore onlay graftu, napravljen je implant od materijala koji sprečava razvoj bakterija, a istovremeno obezbeđuje adekvatnu simetriju lica, fiziološke funkcije i estetski izgled.

266 The most promising material was titanium, since it is anti-bacterial and strong, being lighter than steel, yet heavier than bone tissue, but unfortunately being very expensive. The most important problem with the implant was to keep its low weight and to find a method to manufacture it. The indirect way similar to the production of the cranial implant could be performed by using an investment casting procedure and polistyrole core (prime-model of the implant). The problem is that only a few laboratories can be found that can successfully cast Ti alloys besides, a much better solution was to design an implant in approximately the same way as the cranial one, but producing it directly by means of Selective Laser Melting. Following the DICOM to STL data conversion, CAD modelling of the implant was performed using several three-dimensional modelling and STL manipulation software packages. The idea was to split the skull in two parts in the middle, mirror the right, healthy, side over the left one and obtain the three-dimensional model of the required implant through Boolean subtraction operations. However, due to the facial bone asymmetry the subtracted model could only be used as a reference for further modelling using three-dimensional software After the final inspection of the three-dimensional model, real models of the skull and implant were produced out of polyamide using the SLS and PolyJet processes. The models were used for testing dimensional accuracy and to be analysed by the surgeon. The CAD model of the implant was later changed as required by the surgeon who considered the muscle positions and practical demands of the surgical procedure. It was then sent to the SLM machine to be produced out of Ti6Al4V ELI alloy. The weight of the implant was approx. 6 g, which was quite acceptable, but the compromise was providing it with cca 0,7 mm thin walls, since the desired 0,2 mm walls were too thin for the state of the art SLM procedure13. Our conclusions are that presented case studies show the great potential of RP and RM technologies in medical applications. These were the first cases of RP and RT implant production and implantation in Slovenia. Although the procedure itself is not new it opens new horizons for surgery as well as for engineering and industrial applications. Cranioplastic and maxillofacial surgery is not the only area where surgeon and patient can benefit from custom-made implants. Custom-made bespoke implants not only technically improve the procedure, they can also release some stress by enabling effective pre-surgical planning and simulation as well as reduce costs and, most importantly, decrease morbidity and mortality of patients by means of shortening the time of anaesthesia, time of the surgical procedure, by decreasing infection complications, etc. In the modern era challenges in contemporary medicine can be satisfactory answered only in collaboration with contemporary technological innovation and progress what is of utmost importance in the area of reconstructive surgery.


Materijal koji obećava je titanijum, jer ima antibakterijska svojsta i potrebnu jačinu, a istovremeno je lakši od čelika a teži od kosti. Međutim, ovaj materijal je veoma skup. Najznačajniji problem kod implanta je bio da se postigne lakoća i nađe način izrade. Indirektni način sličan izradi kranijalnog implanta mogao je biti primenjen pomoću procedure ulaganja i jezgra od polistirola (primarni model implanta). Problem je bio što je samo nekoliko laboratorija moglo to da uradi uspešno, a osim toga, mnogo bolje rešenje bilo je da se dizajnira implant otprilike na isti način kao i kranijalni, ali da se izradi direktno pomoću selektivnog laserskog topljenja. Posle DICOM konverzije u STL podatke, CAD modeliranje implanta urađeno je pomoću nekoliko softverskih paketa za 3D modeliranje i STL obradu. Ideja je bila da se lobanja podeli na dva dela po sredini, preklopi desna zdrava polovina preko leve i dobije 3D model željenog implanta primenom Boolean suptrakcije. Međutim, zbog koštane asimetrije lica, rezultirajući model je mogao biti korišćen jedino kao referenca za dalje modeliranje u 3D softveru. Posle finalne inspekcije 3D modela, realni modeli lobanje i implanta su izrađeni od poliamida primenom SLS i PolyJet procesa. Modeli su bili korišćeni za probu dimenzionalne preciznosti i za analizu od strane hirurga. CAD model implanta je kasnije izmenjen po zahtevu hirurga koji je razmotrio poziciju mišića i praktične zahteve hirurške procedure. Model ja zatim upućen u SLM mašinu za izradu implanta od Ti 6 Al 14 V ELI legure. Težina implanta je iznosila oko 6 g, što je bilo prihvatljivo, ali je zbog toga kompromis morao biti u vidu oko 0.7 mm debljine zidova, jer bi željeni zidovi od 0.2 mm bili pretanki za savremenu SLM proceduru. 13 Naši zaključci su da prikazani slučajevi pokazuju veliki potencijal BIP i TBI za medicinsku primenu. Ovo su prvi slučajevi BIP i TBI izrade implanata u Sloveniji. Iako procedura nije nova, otvara nove horizonte u hirurgiji, kao i inženjerstvu i industriji. Kranioplastična i maksilofacijalna hirurgija nisu jedine oblasti gde hirurg i pacijent mogu imati koristi od namenski izrađenih implanata. Ovakvi implanti ne samo da tehnički unapređuju proceduru nego i smanjuju stres, omogućavajući prehirurško planiranje i simulaciju, a takođe smanjuju troškove i, što je najvažnije, morbiditet i mortalitet skraćivanjem trajanja anestezije, hirurške procedure, prevencijom bakterijske infekcije itd. U modernoj eri, izazovi u savremenoj medicini mogu biti adekvatno rešeni samo u saradnji savremenih tehnoloških inovacija i napretka, a što je od presudnog značaja u oblasti rekostruktivne hirurgije.

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Address for corespondence Drstvensek Igor University of Maribor, Faculty of Mechanical Engineering, SI-2000 Maribor, Slovenia +386 2 220 7593 +386 51 694 050 e-mail: [email protected]

Adresa za korespodenciju Drstvensek Igor Univerzitet u Mariboru, Mašinski fakultet 20000 Maribor, Slovenia +386 2 220 7593 +386 51 694 050 e-mail: [email protected]

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